1. Field of the Invention
The present invention relates to a circuit device having a structure in which a flip chip and an interposer substrate are molded and a method of manufacturing the same.
2. Description of the Related Art
Conventional circuit devices such as an IC (integrated circuit) have been manufactured in the form of separate chip components for use in a variety of electronic instruments. In such a circuit device, a multiplicity of lead terminals are provided about a flip chip of a semiconductor circuit which has a plurality of connecting pads. These lead terminals and the connecting pads are connected by bonding wires, and the flip chip and inward portions of the lead terminals are molded with a resin material. In conventional circuit device having the above structure, the lead terminals project outwardly from the edge of the resin material. Therefore, when the circuit device is mounted on a printed circuit board (PCB) so that the lead terminals are connected to printed patterns, data transmission between a semiconductor circuit of the circuit device and the printed circuit board can be carried out.
However, since the circuit devices are now made smaller in the size and higher in the integration so that the number and density of lead terminals are increased, it becomes difficult for a user to precisely connect the lead terminals to the printed patterns of the printed circuit board. Additionally, the lead terminals are too narrow to have an improper degree of physical strength and may be often damaged or injured when the circuit device is handled.
For solving the foregoing problems, a BGA (ball grid array) package has been developed for protecting the circuit device. In such a BGA package, connecting leads are provided as spherical solder bumps which are arrayed in two dimensions over the lower surface of the device. Therefore, the density of the lead terminals is decreased to avoid damage to the lead terminals.
An example of the conventional circuit device having such a BGA structure will be described with reference to FIGS. 1 and 2. FIG. 1 is a schematic cross sectional view of the internal structure of a BGA package in the circuit device. FIG. 2 is a flowchart schematically showing an example of the conventional method of manufacturing the BGA package. For simplification of the description, the upward and downward directions in the drawings shall represent the upward and downward directions on the circuit device.
As shown in FIG. 1, the BGA package 1 includes a flip chip 2 in which a semiconductor circuit is integrated in a high density. The flip chip 2 is mounted above the upper surface of an interposer substrate 3. The flip chip 2 has a multiplicity of connecting pads 4 provided on the lower surface thereof. Also, the interposer substrate 3 has a multiplicity of connecting pads 5 and 6 provided on the upper and lower surfaces thereof. More specifically, an array of the connecting pads 5 are mounted in a higher density on a central region of the upper surface of the interposer substrate 3 at the positions corresponding to the connecting pads 4 of the flip chip 2, while an array of the connecting pads 6 are mounted in lower density on substantially the entire lower surface of the interposer substrate 3. The interposer substrate 3 has a multi-layer structure in which printed wire patterns and through holes provided on its both surfaces and in the inside. The connecting pads 5 on the upper surface are connected to the connecting pads 6 on the lower surface by the printed wire patterns and the through holes.
The connecting pads 5 and 6 are coupled to solder bumps 7 and 8. By the solder bumps 7, the connecting pads 5 on the upper surface of the interposer substrate 3 are mechanically and electrically connected to the connecting pads 4 on the lower surface of the flip chip 2. The space between the solder bumps 7 is filled with an under-fill resin 9 of epoxy resin which enhances the mechanical coupling between the lower surface of the flip chip 2 and the upper surface of the interposer substrate 3.
The BGA package 1 of the example has side wall metal stiffeners 10 which are coupled to on the upper surface of the interposer substrate 3 in a peripheral portion of the flip chip 2. In addition, a top cover or metal heat spreader 11 is mounted over and joined to the upper surfaces of the stiffeners 10 and the flip chip 2 by resign and metal paste 12, respectively.
The flip chip 2 in the BGA package 1 of the conventional circuit device includes a high-density semiconductor circuit with the connecting pads 4 arrayed in the higher density. Each of the connecting pads 4 arrayed in the higher density on the lower surface of the flip chip 2 is connected by the solder bump 7 to corresponding one of the connecting pads 5 arrayed on the upper surface of the interposer substrate 3. The connecting pads 5 are in turn connected to their corresponding connecting pads 6 arrayed in a lower density on the lower surface of the interposer substrate 3. The connecting pads 6 arrayed in the lower density on the lower surface of the interposer substrate 3 in the BGA package 1 are preliminarily provided at their surfaces with solder bumps 8, respectively. This allows the circuit device to be surface-mounted to a circuit board (not shown) of an electronic instrument with ease on the user side, preventing its connecting leads from being physically injured and protecting the BGA package 1.
A conventional method of manufacturing the example of the BGA package will be described in brief. The method starts with preparing relevant components of the BGA package 1 including the flip chip 1, the interposer substrate 3, the stiffeners 10, and the heat spreader 11.
Next, the stiffeners 10 are bonded to the upper surface of the interposer substrate 3 in the peripheral portion and the flip chip 2 is mounted by the solder bumps 7 to the upper surface of the interposer substrate 3 in the central region. After flux is rinsed out, a resultant assembly is dried and subjected to O2 plasma process. The space between the flip chip 2 and the interposer substrate 3 is filled with epoxy resin. The epoxy resin is hardened to produce the under-fill resin 9.
Next, the upper surface of the flip chip 2 is coated by metal paste 12 while the upper surfaces of the stiffeners 10 are coated with an adhesive such as epoxy resin. Then, the heat spreader 11 is bonded to the flip chip 2 and the stiffeners 10. Finally, the connecting pads 6 on the lower surface of the interposer substrate 3 are joined with the solder bumps 8. Thus, the BGA package 1 is completed.
The BGA package 1 manufactured in the above manner has as connecting terminals, the solder bumps 8 arrayed in the lower density in two dimensions on the lower surface thereof. Accordingly, the BGA package 1 can easily be surface-mounted to a printed circuit board on the user side while its connecting terminals are hardly injured.
However, as described above, the under-fill resin 9 filled for enhancing the mechanical bonding strength between the flip chip 2 and the interposer substrate 3 during the fabrication of the BGA package 1. For this filling, a considerable length of time is required for the epoxy resin of a high viscosity to infiltrate into the space by its capillary effect. At this time, the contact area of the under-fill resin 9 with the flip chip 2 and the interposer substrate 3 may not be enough large to increase the coupling strength.
Also, in the above BGA package 1, the interposer substrate 3 and the stiffeners 10 are separately manufactured, and then coupled to each other by the epoxy resin. Then, the heat spreader 11 is coupled to the stiffeners 10 by the epoxy resin. As a result, both the number of manufacturing steps and the number of components are increased, resulting in low productivity. Moreover, the interposer substrate 3, the stiffeners 10, and the heat spreader 11 are joined in a sequence as described above. This may discourage the mechanical bonding strength. As the number of bonding locations is increased, the probability of peeling-off and defect may not be decreased.
Also, the heat spreader 11 of a flat sheet is mounted to the upper surfaces of the flip chip 2 and the stiffeners 10. For the purpose, it is ssential that the surface of the flip chip 2 is aligned with the surfaces of the stiffeners 10. Hence, the productivity of the BGA package 1 is also reduced.
Since the flip chip 2 and the stiffener 10 are separately manufactured as different components, there is sometimes a case that the surface of the flip chip 2 is aligned with the surfaces of the stiffener 10. At that time, they may hardly be coupled at desired accuracy with the heat spreader 11, resulting in causing fabrication fault.
In conjunction with the above description, a chip size package is disclosed in Japanese Laid Open Patent Application (JP-A-Heisei 9-064236). In this reference, a chip (10) is flip-chip-connected to a laminate based substrate (20) with the same size as the chip (10) through direct through-holes (30). A gap between the chip (10) and the substrate (20) is filled with an under-fill (40), and the chip (10) is connected to external terminals (50) through the wiring lines (21 to 24) and via-holes (31). Then, a surface of the substrate is covered by encapsulant (60) other than openings (61). Thus, a high density area array connection is made possible, and delay and noise are reduced through use of low dielectric constant material and shortening of internal wiring length. Also, endurance and humidity resistance are improved by the under-fill and encapsulant.
Also, a semiconductor device is disclosed n Japanese Laid Open Patent Application (JP-A-Heisei 9-293808). In this reference, a semiconductor chip (2) is mounted on a circuit substrate (3) using flip chip bonding technique. A heat emitting fin (4) is provided to be thermally connected to the semiconductor chip (2). Supporting members (6) are provided in a peripheral portion of the portion of the substrate (3) where the semiconductor chip (2) is mounted. The heat emitting fin (4) is supported by the supporting members (6) and the semiconductor chip (2).
Also, a semiconductor device is disclosed in Japanese Laid Open Patent Application (JP-A-Heisei 11-097570). In this reference, a semiconductor chip (1) has a main surface on which a semiconductor circuit is formed, and gold bumps (39 are formed. A metal piece (2a) has a connection terminal section (2b) electrically connected to the gold bump (3) and an external terminal section (2c) electrically connected to the connection terminal section (2b). A sealing section (4) is used to seal the semiconductor chip (1) and the gold bumps (3). Thus, the semiconductor chip (1) is flip-chip-connected to the metal pieces (2a) via the gold bumps (3).
Therefore, an object of the present invention is to provide a circuit device in which the number of relevant components can be reduced so that the productivity of the circuit device is improved.
Another object of the present invention is to provide a circuit device in which the junction strength between a flip chip and an interposer substrate can be increased.
Still another object of the present invention is to provide a circuit device in which the junction strength between an interposer substrate and a heat spreader can be increased.
Yet still another object of the present invention is to provide a circuit device in which a heat spreader is held by mold resin.
It is also an object of the present invention to provide a method of manufacturing any of the above mentioned circuit devices.
In order to achieve an aspect of the present invention, a circuit device with a ball grid array (BGA) package structure includes an interposer substrate, at least a flip chip, a unitary mold resin and a heat spreader. The interposer substrate has a plurality of first connecting pads arrayed on an upper surface thereof in a first density. The flip chip has a plurality of second connecting pads arrayed on a lower surface thereof in the first density, and is mounted on the interposer substrate via solder bumps for connecting the plurality of first connecting pads and the plurality of second connecting pads. The unitary mold resin fills a space between the lower surface of the flip chip and the upper surface of the interposer substrate and peripheral portions of the flip chip on the upper surface of the interposer substrate. The heat spreader has a lower surface coupled to an upper surface of the flip chip and upper surfaces of the peripheral portions.
The interposer substrate has a plurality of third connecting pads arrayed on a lower surface thereof in a second density lower than the first density, and solder balls are connected to the plurality of third connecting pads.
Also, the heat spreader may be coupled to the flip chip with metal paste and the upper surfaces of the peripheral portions with resin. Alternatively, the heat spreader may be coupled to the flip chip with metal paste and directly coupled to the upper surfaces of the peripheral portions. Instead, the heat spreader may be directly coupled to the flip chip and the upper surfaces of the peripheral portions.
Also, the heat spreader may be smaller than the interposer substrate in size. In this case, the heat spreader is desirably connected to the unitary mold resin at side surfaces of the heat spreader. In addition, the heat spreader is desirably covered with a portion of the unitary mold resin at edge portions of an upper surface of the heat spreader.
Also, it is desirable that the heat spreader has small openings on the lower surface thereof, and the small openings are filled with a part of the unitary mold resin. Also, the heat spreader has a plurality of recess portions on the lower surface thereof, and the plurality of recess portions are filled with a part of the unitary mold resin.
In another aspect of the present invention, a method of manufacturing a circuit device with a ball grid array (BGA) package structure, is attained by mounting at least a flip chip on an interposer substrate via solder bumps which connect a plurality of first connecting pads and a plurality of second connecting pads to produce a mounted assembly, wherein the plurality of first connecting pads are provided on an upper surface of the interposer substrate and the plurality of second connecting pads are provided on a lower surface of the flip chip; by setting the mounted assembly in a cavity formed by molds such that an upper surface of the flip chip and the lower surface of the interposer substrate are in contact with walls of the cavity; by forming a unitary mold resin by injecting a resin into the cavity such that the resin fills a space between the lower surface of the flip chip and the upper surface of the interposer substrate and peripheral portions of the flip chip on the upper surface of the interposer substrate; and by coupling a heat spreader to the upper surface of the flip chip and upper surfaces of the peripheral portions.
When the interposer substrate has a plurality of third connecting pads arrayed on a lower surface thereof, the method may further include: connecting solder balls to the plurality of third connecting pads.
Also, the coupling includes: coupling the heat spreader to the flip chip with metal paste and the upper surfaces of the peripheral portions with resin.
Also, when the heat spreader has small openings on the lower surface thereof, the forming may include: filling the small openings with the resin.
Also, when the heat spreader has a plurality of recess portions on the lower surface thereof, the forming may include: filling the plurality of recess portions with the resin.
In still another aspect of the present invention, a method of manufacturing a circuit device with a ball grid array (BGA) package structure, is attained by mounting at least a flip chip on an interposer substrate via solder bumps which connect a plurality of first connecting pads and a plurality of second connecting pads, wherein the plurality of first connecting pads are provided on an upper surface of the interposer substrate and the plurality of second connecting pads are provided on a lower surface of the flip chip; by coupling a heat spreader to the upper surface of the flip chip to produce a mounted assembly; by setting the mounted assembly in a cavity formed by molds such that an upper surface of the flip chip and the lower surface of the interposer substrate are in contact with walls of the cavity; and by forming a unitary mold resin by injecting a resin into the cavity such that the resign fills a space between the lower surface of the flip chip and the upper surface of the interposer substrate and peripheral portions of the flip chip on the upper surface of the interposer substrate.
Here, when the interposer substrate has a plurality of third connecting pads arrayed on a lower surface thereof, the method may further includes: connecting solder balls to the plurality of third connecting pads.
Also, the coupling may include: coupling heat spreader to the upper surface of the flip chip with metal paste. Instead, the heat spreader may be directly coupled to the flip chip and the upper surfaces of the peripheral portions.
Also, when the heat spreader is smaller than the interposer substrate in size, the heat spreader is connected to the unitary mold resin at side surfaces of the heat spreader. In this case, the heat spreader may be covered with a portion of the unitary mold resin at edge portions of an upper surface of the heat spreader. Also, when the heat spreader has small openings on the lower surface thereof, the forming may include: filling the small openings with the resin.
Also, when the heat spreader has a plurality of recess portions on the lower surface thereof, the forming may include: filling the plurality of recess portions with the resin.